Power monitoring device for identifying state of electric appliance and power monitoring method thereof

A power monitoring system for identifying a state of an electric appliance, comprising:

• a first power monitoring device, for measuring a power consumption feature of a first power supply, so as to detect and calculate a first variation of the power consumption feature of the first power supply, wherein the first power supply supplies electric power to a first electric appliance group and a second electric appliance group;
• and
• at least one second power monitoring device, for measuring a power consumption feature of a corresponding second power supply, so as to detect and calculate a second variation of the power consumption feature of the second power supply, wherein the second power supply is a branch of the first power supply and supplies electric power to the second electric appliance group,
• wherein the first power monitoring device and the second power monitoring device perform a level construction step to obtain a relative position between the first power monitoring device and the second power monitoring device and synchronously calibrate the first variation and the second variation to calculate a first electric appliance variation, when the first electric appliance variation is detected, the first power monitoring device searches an electric appliance signature database according to the first electric appliance variation to obtain and monitor states of a plurality of first electric appliances corresponding to the first electric appliance variation or a combination of the states of the first electric appliances, wherein the first electric appliance group comprise the first electric appliances.